In information storage systems, such as disc drives found in personal computers and other data processing devices, a magnetic storage medium is moved relative to a read/write head to provide information introduction to and/or retrieval from the magnetic storage medium. The magnetic storage medium (also referred to as a "disc" or "media") is typically comprised of a rigid substrate, an underlayer, a magnetic layer and a sputtered carbon layer atop the magnetic layer. In the design of such devices, it is most desirable from a magnetic standpoint to have the read/write head fly very close to the surface of the disc during movement to maximize the signal quality. Flying to low however, can cause wear and material interactions on the surface of the disc which lead to poor system reliability and performance. To reduce such wear and material interactions, a lubricant is commonly disposed on the surface of the disc.
Magnetic thin film discs typically require a barrier lubricant, which is generally applied on top of the sputtered carbon protective film, to reduce the wear of the interface between the read-write head and the disc during start stop cycles. The mechanical properties of the sputtered carbon film can be varied by incorporation of other elements during its preparation, such as hydrogen and nitrogen. Thus, the chemical interactions between the lubricant and the chemically modified carbon film are very important for the tribological properties of the carbon/lubricant system.
In particular, the lubricant should adhere strongly to the carbon film (represented by the bonded lube ratio), and should wet the film uniformly. Failure to wet the film uniformly could cause droplet formation and result in lubricant transfer to the read-write head during operation. In addition, if the lubricant is too volatile, it may transfer to the read-write head through the vapor phase. If enough lubricant is transferred to the head by these mechanisms, it could flood the head-disc interface when the drive is shut down, and the high value of static friction at the flooded interface could cause a drive failure (fly stiction). For the same reason, the lubricant should adhere strongly enough to the carbon film that it does not migrate and flood the head-disc interface during extended periods of operation. On the other hand, if the lubricant is so strongly bound that it does not replenish itself during drive operation, unacceptably high wear rates could result.
Further, the lubricant should by thermally and chemically stable, and exhibit the ability to resist decomposition over time, such as decomposition by acid catalysis. Conventional lubricants that contain formyl and difluoroformyl linkages in their backbone are subject to decomposition over time because the linkages are cleaved by acid catalysis. Thus, there is a continuing interest in the development of improved lubricants that exhibit good lubricating and tribological properties including wear resistance, low stiction, high bonded lube ratios and resistance to decomposition over time.